Northcott's game is Nim in disguise

Northcott's game puts a black and a white piece on each row of a board; on your turn you slide your piece along its row without jumping the opponent's. It looks new, but it is Nim in disguise. The gap between the two pieces on a row is a Nim heap, and sliding your piece toward the opponent shrinks that gap, exactly like removing counters.

Moving away from the opponent grows a gap, but that never helps: the opponent can simply undo it, so those moves do not change the outcome. Read the gaps as heaps and play the Nim strategy on them.